(window.webpackJsonp=window.webpackJsonp||[]).push([[1762],{2170:function(t,a,s){"use strict";s.r(a);var n=s(31),e=Object(n.a)({},(function(){var t=this,a=t.$createElement,s=t._self._c||a;return s("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[s("h1",{attrs:{id:"method-chaining"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#method-chaining"}},[t._v("#")]),t._v(" Method Chaining")]),t._v(" "),s("h2",{attrs:{id:"chainable-object-design-and-chaining"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#chainable-object-design-and-chaining"}},[t._v("#")]),t._v(" Chainable object design and chaining")]),t._v(" "),s("p",[t._v("Chaining and Chainable is a design methodology used to design object behaviors so that calls to object functions return references to self, or another object, providing access to additional function calls allowing the calling statement to chain together many calls without the need to reference the variable holding the object/s.")]),t._v(" "),s("p",[t._v("Objects that can be chained are said to be chainable. 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function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("             "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// console output "1 : 1"')]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("clone")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("           "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// returns a new instance of the object")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("scale")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("          "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// from which you can continue chaining")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n\n")])])]),s("h3",{attrs:{id:"don-t-create-ambiguity-in-the-return-type"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#don-t-create-ambiguity-in-the-return-type"}},[t._v("#")]),t._v(" Don't create ambiguity in the return type")]),t._v(" "),s("p",[t._v("Not all function calls return a useful chainable type, nor do they always return a reference to self. This is where common sense use of naming is important. In the above example the function call "),s("code",[t._v(".clone()")]),t._v(" is unambiguous. Other examples are "),s("code",[t._v(".toString()")]),t._v(" implies a string is returned.")]),t._v(" "),s("p",[t._v("An example of an ambiguous function name in a chainable object.")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v("\n// line object represents a line\n line.rotate(1)\n    .vec();  // ambiguous you don't need to be looking up docs while writing.\n\n line.rotate(1)\n    .asVec()    // unambiguous implies the return type is the line as a vec (vector)\n    .add({x:10,y:10)\n // toVec is just as good as long as the programmer can use the naming \n // to infer the return type\n\n")])])]),s("h3",{attrs:{id:"syntax-convention"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#syntax-convention"}},[t._v("#")]),t._v(" Syntax convention")]),t._v(" "),s("p",[t._v("There is no formal usage syntax when chaining. The convention is to either chain the calls on a single line if short or to chain on the new line indented one tab from the referenced object with the dot on the new line.  Use of the semicolon is optional but does help by clearly denoting the end of the chain.")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v("\n vec.scale(2).add({x:2,y:2}).log();  // for short chains\n\n  vec.scale(2)     // or alternate syntax\n      .add({x:2,y:2})\n      .log();  // semicolon makes it clear the chain ends here\n\n  // and sometimes though not necessary\n  vec.scale(2)     \n      .add({x:2,y:2})\n      .clone()    // clone adds a new reference to the chain\n           .log(); // indenting to signify the new reference\n\n  // for chains in chains\n  vec.scale(2)     \n      .add({x:2,y:2})\n      .add(vec1.add({x:2,y:2})  // a chain as an argument \n           .add({x:2,y:2})      // is indented\n           .scale(2))\n      .log();\n\n  // or sometimes \n  vec.scale(2)     \n      .add({x:2,y:2})\n      .add(vec1.add({x:2,y:2})  // a chain as an argument \n           .add({x:2,y:2})      // is indented\n           .scale(2)\n      ).log();   // the argument list is closed on the new line\n\n")])])]),s("h3",{attrs:{id:"a-bad-syntax"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#a-bad-syntax"}},[t._v("#")]),t._v(" A bad syntax")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v("\n  vec          // new line before the first function call\n      .scale()  // can make it unclear what the intention is\n      .log();\n\n   vec.          // the dot on the end of the line\n      scale(2).  // is very difficult to see in a mass of code\n      scale(1/2); // and will likely frustrate as can easily be missed\n                  // when trying to locate bugs\n\n")])])]),s("h3",{attrs:{id:"left-hand-side-of-assignment"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#left-hand-side-of-assignment"}},[t._v("#")]),t._v(" Left hand side of assignment")]),t._v(" "),s("p",[t._v("When you assign the results of a chain the last returning call or object reference is assigned.")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v("\nvar vec2 = vec.scale(2)\n                .add(x:1,y:10)\n                .clone();   // the last returned result is assigned\n                                // vec2 is a clone of vec after the scale and add\n\n")])])]),s("p",[t._v("In the above example "),s("code",[t._v("vec2")]),t._v(" is assigned the value returned from the last call in the chain. 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